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Title: Geology of the Source Physics Experiment Site, Climax Stock, Nevada National Security Site

Abstract

A test bed for a series of chemical explosives tests known as Source Physics Experiments (SPE) was constructed in granitic rock of the Climax stock, in northern Yucca Flat at the Nevada National Security Site in 2010-2011. These tests are sponsored by the U.S. Department of Energy, National Nuclear Security Administration's National Center for Nuclear Security. The test series is designed to study the generation and propagation of seismic waves, and will provide data that will improve the predictive capability of calculational models for detecting and characterizing underground explosions. Abundant geologic data are available for the area, primarily as a result of studies performed in conjunction with the three underground nuclear tests conducted in the Climax granite in the 1960s and a few later studies of various types. The SPE test bed was constructed at an elevation of approximately 1,524 meters (m), and consists of a 91.4-centimeter (cm) diameter source hole at its center, surrounded by two rings of three 20.3-cm diameter instrument holes. The inner ring of holes is positioned 10 m away from the source hole, and the outer ring of holes is positioned 20 m from the source hole. An initial 160-m deep core hole was drilledmore » at the location of the source hole that provided information on the geology of the site and rock samples for later laboratory testing. A suite of geophysical logs was run in the core hole and all six instruments holes to obtain matrix and fracture properties. Detailed information on the character and density of fractures encountered was obtained from the borehole image logs run in the holes. A total of 2,488 fractures were identified in the seven boreholes, and these were ranked into six categories (0 through 5) on the basis of their degree of openness and continuity. The analysis presented here considered only the higher-ranked fractures (ranks 2 through 5), of which there were 1,215 (approximately 49 percent of all fractures identified from borehole image logs). The fractures were grouped into sets based on their orientation. The most ubiquitous fracture set (50 percent of all higher-ranked fractures) is a group of low-angle fractures (dips 0 to 30 degrees). Fractures with dips of 60 to 90 degrees account for 38 percent of high-ranked fractures, and the remaining 12 percent are fractures with moderate dips (30 to 60 degrees). The higher-angle fractures are further subdivided into three sets based on their dip direction: fractures of Set 1 dip to the north-northeast, fractures of Set 2 dip to the south-southwest, and Set 3 consists of high-angle fractures that dip to the southeast and strike northeast. The low-angle fractures (Set 4) dip eastward. Fracture frequency does not appear to change substantially with depth. True fracture spacing averages 0.9 to 1.2 m for high-angle Sets 1, 2, and 3, and 0.6 m for Set 4. Two significant faults were observed in the core, centered at the depths of 25.3 and 32.3 m. The upper of these two faults dips 80 degrees to the north-northeast and, thus, is related to the Set-1 fractures. The lower fault dips 79 degrees to the south-southwest and is related to SPE Set-2 fractures. Neither fault has an identifiable surface trace. Groundwater was encountered in all holes drilled on the SPE test bed, and the fluid level averaged about 15.2 to 18.3 m below ground surface. An informal study of variations in the fluid level in the holes conducted during various phases of construction of the test bed concluded that groundwater flow through the fractured granitic rocks is not uniform, and appears to be controlled by variations in the orientation and degree of interconnectedness of the fractures. It may also be possible that an aplite dike or quartz vein may be present in the test bed, which could act as a barrier to groundwater flow and, thus, could account for anisotropy seen in the groundwater recovery measurements.« less

Authors:
Publication Date:
Research Org.:
Nevada Test Site/National Security Technologies, LLC (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1036766
Report Number(s):
DOE/NV/25946-1448
TRN: US201207%%407
DOE Contract Number:
DE-AC52-06NA25946
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; ANISOTROPY; APLITES; BOREHOLES; CHEMICAL EXPLOSIVES; CONSTRUCTION; FLUID FLOW; FRACTURE PROPERTIES; FRACTURES; GEOLOGY; GRANITES; GROUND WATER; QUARTZ; SEISMIC WAVES; SOLAR PROTONS; TESTING; UNDERGROUND EXPLOSIONS; WAVE PROPAGATION; Geology, Source Physics Experiment Site, Climax Stock, Nevada National Security Site

Citation Formats

Townsend, M., Prothro, L. B., Obi, C. Geology of the Source Physics Experiment Site, Climax Stock, Nevada National Security Site. United States: N. p., 2012. Web. doi:10.2172/1036766.
Townsend, M., Prothro, L. B., Obi, C. Geology of the Source Physics Experiment Site, Climax Stock, Nevada National Security Site. United States. doi:10.2172/1036766.
Townsend, M., Prothro, L. B., Obi, C. Thu . "Geology of the Source Physics Experiment Site, Climax Stock, Nevada National Security Site". United States. doi:10.2172/1036766. https://www.osti.gov/servlets/purl/1036766.
@article{osti_1036766,
title = {Geology of the Source Physics Experiment Site, Climax Stock, Nevada National Security Site},
author = {Townsend, M., Prothro, L. B., Obi, C.},
abstractNote = {A test bed for a series of chemical explosives tests known as Source Physics Experiments (SPE) was constructed in granitic rock of the Climax stock, in northern Yucca Flat at the Nevada National Security Site in 2010-2011. These tests are sponsored by the U.S. Department of Energy, National Nuclear Security Administration's National Center for Nuclear Security. The test series is designed to study the generation and propagation of seismic waves, and will provide data that will improve the predictive capability of calculational models for detecting and characterizing underground explosions. Abundant geologic data are available for the area, primarily as a result of studies performed in conjunction with the three underground nuclear tests conducted in the Climax granite in the 1960s and a few later studies of various types. The SPE test bed was constructed at an elevation of approximately 1,524 meters (m), and consists of a 91.4-centimeter (cm) diameter source hole at its center, surrounded by two rings of three 20.3-cm diameter instrument holes. The inner ring of holes is positioned 10 m away from the source hole, and the outer ring of holes is positioned 20 m from the source hole. An initial 160-m deep core hole was drilled at the location of the source hole that provided information on the geology of the site and rock samples for later laboratory testing. A suite of geophysical logs was run in the core hole and all six instruments holes to obtain matrix and fracture properties. Detailed information on the character and density of fractures encountered was obtained from the borehole image logs run in the holes. A total of 2,488 fractures were identified in the seven boreholes, and these were ranked into six categories (0 through 5) on the basis of their degree of openness and continuity. The analysis presented here considered only the higher-ranked fractures (ranks 2 through 5), of which there were 1,215 (approximately 49 percent of all fractures identified from borehole image logs). The fractures were grouped into sets based on their orientation. The most ubiquitous fracture set (50 percent of all higher-ranked fractures) is a group of low-angle fractures (dips 0 to 30 degrees). Fractures with dips of 60 to 90 degrees account for 38 percent of high-ranked fractures, and the remaining 12 percent are fractures with moderate dips (30 to 60 degrees). The higher-angle fractures are further subdivided into three sets based on their dip direction: fractures of Set 1 dip to the north-northeast, fractures of Set 2 dip to the south-southwest, and Set 3 consists of high-angle fractures that dip to the southeast and strike northeast. The low-angle fractures (Set 4) dip eastward. Fracture frequency does not appear to change substantially with depth. True fracture spacing averages 0.9 to 1.2 m for high-angle Sets 1, 2, and 3, and 0.6 m for Set 4. Two significant faults were observed in the core, centered at the depths of 25.3 and 32.3 m. The upper of these two faults dips 80 degrees to the north-northeast and, thus, is related to the Set-1 fractures. The lower fault dips 79 degrees to the south-southwest and is related to SPE Set-2 fractures. Neither fault has an identifiable surface trace. Groundwater was encountered in all holes drilled on the SPE test bed, and the fluid level averaged about 15.2 to 18.3 m below ground surface. An informal study of variations in the fluid level in the holes conducted during various phases of construction of the test bed concluded that groundwater flow through the fractured granitic rocks is not uniform, and appears to be controlled by variations in the orientation and degree of interconnectedness of the fractures. It may also be possible that an aplite dike or quartz vein may be present in the test bed, which could act as a barrier to groundwater flow and, thus, could account for anisotropy seen in the groundwater recovery measurements.},
doi = {10.2172/1036766},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2012},
month = {Thu Mar 15 00:00:00 EDT 2012}
}

Technical Report:

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  • The Source Physics Experiment (SPE) will involve a series of explosions in various geologic and emplacement conditions to validate numerical simulation methods to predict behavior of seismic wave excitation and propagation for nuclear test monitoring. The first SPE's currently underway involve explosions in the Climax Stock (granitic geology) at the Nevada National Security Site (NNSS). Detailed geologic data and published material properties for the major lithologic units of the NNSS and surrounding region were used to build three-dimensional models for seismic wave propagation simulations. The geologic structure near the SPE shot point is quite varied including granitic, carbonate, tuff andmore » alluvium lithologies. We performed preliminary ground motion simulations for a near-source domain covering 8 km x 8 km at the surface centered on the shot point to investigate various source and propagation effects using WPP, LLNL's anelastic seismic wave finite difference code. Simulations indicate that variations in wave propagation properties of the sub-surface will generate strongly path-dependent response once the energy has left the relatively small granitic geology of the near-surface Climax Stock near the SPE shot point. Rough topography to the north and west of SPE shot point causes additional complexity in the signals including energy on the transverse components. Waves propagate much faster through the granitic and carbonate formations and slower through the tuff and alluvium. Synthetic seismograms for a pure explosion source in a 3D geologic structure show large amplitudes on transverse component. For paths to the south sampling the granite, tuff and alluvium lithologies transverse component amplitudes are as high as 50% of that on the vertical and radial components.« less
  • The Source Physics Experiment (SPE) is planning a 1000 kg (TNT equivalent) shot (SPE2) at the Nevada National Security Site (NNSS) in a granite borehole at a depth (canister centroid) of 45 meters. This shot follows an earlier shot of 100 kg in the same borehole at a depth 60 m. Surrounding the shotpoint is an extensive array of seismic sensors arrayed in 5 radial lines extending out 2 km to the north and east and approximately 10-15 to the south and west. Prior to SPE1, simulations using a finite difference code and a 3D numerical model based on themore » geologic setting were conducted, which predicted higher amplitudes to the south and east in the alluvium of Yucca Flat along with significant energy on the transverse components caused by scattering within the 3D volume along with some contribution by topographic scattering. Observations from the SPE1 shot largely confirmed these predictions although the ratio of transverse energy relative to the vertical and radial components was in general larger than predicted. A new set of simulations has been conducted for the upcoming SPE2 shot. These include improvements to the velocity model based on SPE1 observations as well as new capabilities added to the simulation code. The most significant is the addition of a new source model within the finite difference code by using the predicted ground velocities from a hydrodynamic code (GEODYN) as driving condition on the boundaries of a cube embedded within WPP which provides a more sophisticated source modeling capability linked directly to source site materials (e.g. granite) and type and size of source. Two sets of SPE2 simulations are conducted, one with a GEODYN source and 3D complex media (no topography node spacing of 5 m) and one with a standard isotropic pre-defined time function (3D complex media with topography, node spacing of 5 m). Results were provided as time series at specific points corresponding to sensor locations for both translational (x,y,z) and rotational components. Estimates of spectral scaling for SPE2 are provided using a modified version of the Mueller-Murphy model. An estimate of expected aftershock probabilities were also provided, based on the methodology of Ford and Walter, [2010].« less
  • The first Source Physics Experiment shot (SPE-1) was conducted in May 2011. The explosive source was a ~100-kilogram TNT-equivalent chemical set at a depth of 60 meters. It was recorded by an extensive set of instrumentation that includes sensors both at near-field (less than 100 meters) and far-field (more than 100 meters) distances. The near-field instruments consisted of three-component accelerometers deployed in boreholes around the shot and a set of singlecomponent vertical accelerometers on the surface. The far-field network comprised a variety of seismic and acoustic sensors, including short-period geophones, broadband seismometers, three-component accelerometers, and rotational seismometers at distances ofmore » 100 meters to 25 kilometers. This report coincides with the release of these data for analysts and organizations that are not participants in this program. This report describes the first Source Physics Experiment and the various types of near-field and far-field data that are available.« less
  • The Climax stock is a composite stock of Cretaceous age, composed of quartz monzonite and granodiorite, which intrudes sedimentary rocks of Paleozoic and Precambrian age. Tertiary rocks consisting of tuff, welded tuff, and breccia overlie the stock and sedimentary rocks. Hydrothermal alteration of the granodiorite and quartz monzonite is found mainly along joints and is extensive, but the intensity of alteration varies from place to place. The surrounding sedimentary rocks (carbonates) have been metasomatically altered to tactite and marble as much as 1,500 feet (457 m) from contact with stock; the degree of metamorphism decreasing away from the intrusive. Themore » major faults found in the vicinity of the Climax stock are the Tippinip fault, the Boundary fault, and the Yucca fault. In the stock three prominent joint sets and their average attitudes are N. 32/sup 0/ W., 22/sup 0/ NE.; N. 64/sup 0/ W., vertical; and N. 35/sup 0/ E., vertical. Two major tunnel complexes have been driven into the Climax stock, the Tiny Tot tunnel complex and Pile Driver-Hard Hat tunnel complex. In the Pile Driver-Hard Hat tunnel complex two underground nuclear tests have been conducted.« less